The number of women choosing to delay motherhood by freezing their eggs has soared, figures show.

There has been a "substantial increase" in the number of women freezing their eggs to have a child later in life, the Human Fertilisation and Embryology Authority (HFEA) found.

The most common reason given for freezing was having no male partner, according to the HFEA's latest report.

In 2001, just 29 women opted to freeze their eggs but since then there has been a sustained increase, the authority said.

In 2014, 816 opted to delay motherhood and store their eggs for later use - a 25% increase on the previous year.

A third of women aged 37 and under froze their eggs because they had no male partner, with this figure rising to more than half for women aged 38 and over.

Other reasons for freezing eggs include women facing medical treatment that may affect their fertility - such as women undergoing chemotherapy for cancer; those who do not feel ready for motherhood and are concerned about their fertility declining; women who delay motherhood for professional reasons; women who are at risk of injury or death, for instance a member of the armed forces who is about to be deployed to a war zone; or women undergoing gender reassignment.

Freezing eggs has become an increasingly popular way for professional women to stop their biological clock during key years in their careers. Companies such as Apple and Facebook even offer female workers egg freezing as a perk of their job.

Since 2001, 3,676 women have undergone the procedure, figures show.

But fewer than 60 babies have been born to patients storing and thawing their own eggs since 2001, the HFEA said.

The approximate success rate of using frozen eggs was 14%, compared with an average 26% success rate of IVF using fresh eggs, it said.

But the HFEA warned: "The nature of egg freezing means we may not know the true success rate for eggs frozen now for several years to come. The numbers we have now are small and should be used cautiously."

Women are born with a pool of one to two million eggs that decrease in number over time until at the menopause they effectively run out.

But it is not only the number but the quality of eggs that is reduced by the passing years. Over time, a woman's eggs can end up with too many or too few chromosomes - the strands of packaged DNA that contain our genes. The chromosomal abnormalities lead to infertility, stillbirth or birth defects such as Down's syndrome.

"While there has been much made recently about the rise in 'social' egg freezing, the number of frozen eggs actually being used in treatment is still extremely low.

"New freezing techniques appear to have improved the chance of future success, but it's still too early to know that for certain, so it's important that women don't see freezing as a guarantee of future pregnancy."

The HFEA's Fertility Treatment in 2014 - Trends and Figures report also shows a rise in the number of IVF cycles.

In 2014, 52,288 women had a total of 67,708 cycles of IVF, a near 5% year-on-year growth in the number of cycles.

They also noted an increase in success rates - the IVF birth rate increased slightly to 26.5% in 2013 from 25.9% the year before.